Infra-red sensor devices are widely used for sensing and measuring temperature conditions in various industrial and scientific environments. The sensor elements are typically sold as a unit encapsulated in a cylindrical outer case to protect the sensor elements which are usually small, fragile and generally difficult to handle. The case provides physical and mechanical protection for the sensor elements. A sensing face of the infra-red sensor is typically located at one axially end of the cylindrical case, and electrical conductor leads capable of being attached to internal circuitry of the sensor extend from a position typically at or near the opposite end of the cylindrical outer case.
It is known to mount infra-red sensors in fixed locations relative to a test surface or area having a temperature characteristic to be monitored. Mounting typically is accomplished by a bracket having various gripping or clamping devices of well-known design. The bracket or other support is capable of being attached to any suitable, appropriately located surface, such as a fixed portion of a related apparatus, or other structure in which the sensor or related apparatus is enclosed. The sensing face of the sensor is aimed at a desired portion of a surface to be monitored. Generally, the distance between the sensing face and the monitored test surface is selected to control the total amount of surface area that falls within the operable range of the sensor. Accurate positioning relative to the surface to be monitored is required in order to obtain accuracy, reliability and overall usefulness of the sensor signals. The sensor signals are directly dependent on precise determination of the distance between the sensor face and the surface to be monitored. If the distance is greater than intended or less than intended, erroneous temperature readings are likely to result, or the sensor may fail to monitor the proper area of the surface to be monitored.
Known optical temperature measurement devices include a probe having a sensor with temperature-dependent light-absorbing properties. The sensor is in optical communication with a source of light and a detector such as a spectrophotometer. A characteristic factor and a temperature-dependent factor can be derived from measurements of the amount of light transmitted through the sensor by analyzing the change in the absorbance characteristics of the sensor material with changes in temperature. The choice of temperature-sensing materials depends on the desired temperature range and sensitivity of the measurement, and the physical condition expected at the location. The sensor can be made of substantially non-electrically-conducting materials to minimize electrical interference when used in electromagnetic fields and near sources of leakage current. The probe can be made of substantially non-electrically-conducting and non-thermally-conducting materials, minimizing the effects of stray electromagnetic fields, leakage currents, and thermal conductivity on the measurement. Additional information regarding known optical temperature measurement devices and methods can be obtained from U.S. Pat. No. 5,358,396 issued on Sep. 20, 1994 which is incorporated herein by reference. Additional details regarding infra-red thermal couples can be obtained from U.S. Pat. No. 5,399,018 issued Mar. 21, 1995 which is incorporated herein by reference.